Sheet-metal articles can be made by hot blow-forming processes that use complementary forming tools in a press under the pressure of a working gas to stretch-form a preheated sheet-metal blank against heated forming surfaces on the forming tools. Such processes are particularly applicable to forming sheet-metal into products of complex three-dimensional curvature. For example, superplastic-forming (SPF) and quick-plastic-forming (QPF) processes are increasingly being used to produce high quality sheet-metal products such as automotive body panels. One such process is disclosed in U.S. Pat. No. 6,253,588, entitled “Quick Plastic Forming of Aluminum Alloy Sheet-metal” to Rashid et al., which is assigned to the assignee hereof and which is incorporated by reference herein.
While such SPF and QPF processes and equipment generate improved parts, production efficiency has at times been diminished because of the time required to effectively remove parts from forming tools. At elevated forming temperatures on the order of 900° F., a formed sheet-metal panel tends to “stick” to a hot forming surface or seal bead of the forming tool. Attempts to mechanically pry a heat-softened panel from a hot forming tool inevitably result in undesirable distortion of the panel. Various other prior art approaches for extracting a heat-softened panel from a hot forming tool suffer from one or more of the following problems: puncture of the panel, non-uniform or erratic extraction and resulting distortion of the panel, complex extraction equipment requiring auxiliary drives and control mechanisms, and excessive lubricant build-up on the forming tools. Thus, it is an object of this invention to provide an improved apparatus for removing a heat-softened formed panel from hot blow-forming tooling that does not suffer from the foregoing disadvantages of prior art approaches.